Third-Generation Birth Control Pills The "new" pill

It is hard to imagine any medication that has influenced the lives of women more than “the pill." Oral contraceptives were introduced in the early 1960s. They are now used by more than 65 million women worldwide, about six per cent of women of child-bearing age.

From the beginning there has been research and debate about the benefits and side-effects of the birth control pill. The new oral contraceptives are no different. These are the “third generation” pills, which have lower doses of active ingredients than their predecessors. They have been shown to be just as good (if not better) in preventing pregnancy and have reduced side-effects such as irregular menstrual cycle, weight gain and headaches. Why then did the United Kingdom’s Committee on Safety in Medicine caution doctors about their use? Before we answer this question, perhaps a brief explanation on what makes up the pill and how it works is needed.

How does the pill work?

Most birth control pills contain two main ingredients, a form of estrogen and a progestin. These two substances are similar to the female body’s reproductive hormones (estrogen and progesterone) and the body responds to the pill’s hormones in much the same way. The contraceptive effect from the pill comes mainly from the progesterone-like compounds (progestins) in the pill.

Progestins change the mucous produced by the cervix (the passageway between the vagina and the womb or uterus) and make it more difficult for sperm to swim to the egg. If sperm do reach an egg and fertilize it, progestins alter the nutrient layer lining the interior of the uterus to make survival of the egg unlikely. Estrogens in the pill decrease the development of eggs in the ovaries and help prevent eggs from being released by the ovaries (ovulation). Through these mechanisms, the pill has been found to be more than 99.99 per cent effective in preventing pregnancy when taken correctly.

What effect does the pill have on your body?

Research over the last 35 years has shown that besides excellent contraception, the pill can control irregular bleeding and painful periods. It may reduce the occurrence of cancer of the uterus and ovaries by up to 50 per cent. It can decrease uterine fibroid development and limit fibrocystic breast disease and pain. No firm evidence has shown that oral contraceptives either increase or decrease the incidence of breast cancer.

Potential side-effects of the pill include nausea, headaches, fluid retention, increase in body hair, weight gain and gallstone formation. Some types of pills may also raise blood pressure or increase the risk of developing blood clots. The latter are discussed in detail below.

The “third generation” pills

The first generation of birth control pills (developed in the 1960s) used a higher concentration of estrogen-like compounds as the main means of contraception. It was believed at that time that these levels created an unacceptable risk of the formation of blood clots in the legs. Thus, second generation oral contraceptives were introduced. They included progestins at varying concentrations and strengths. Some of these preparations use gradually increasing doses of hormones over three phases, resulting in a lower total dosage of hormone each month.

In the 1990s the third generations of oral contraceptives were released. They contain the new progestins Gestodene™, Desogestrel™ and Norgestimate™. These contraceptives have lower doses of progesterone-like compounds with similar protection against pregnancy. As well, they have been shown to have fewer side effects such as weight gain, fluid retention, headaches and unwanted hair growth.

In 1995, a research team in Montreal led by a McGill University professor discovered that these third generation pills may be linked to a higher risk of forming blood clots in the legs, medically known as “deep venous thrombosis” or DVT. This sent the European Medical Community spinning, as use of the new oral contraceptives in Europe was quite high. As similar results were obtained from several other studies, the European Safety in Medicine Committee warned against their use. Now, before you scramble to see if your birth control pills contain one of the above progestins, let us carefully examine the evidence.

It has long been known that women taking the pill have a four times greater risk of developing blood clots than non-users – about 1.5 DVTs for every 10,000 users. However, pregnancy also puts women at much higher risk for DVTs - about six women for every 10,000 pregnancies. The risk of DVT is 16 times higher for pregnant women than non-pregnant women.

Recent studies published in several respected medical journals have reported that third generation pills increase the risk of DVTs anywhere from 1.5 to three times when compared to second generation progestins. It appears this effect is most marked for women who have a past history of blood clots, a strong family history of DVTs or are overweight. It is important to note the increase in DVTs due to third generation progestin pills was not associated with Norgestimate™. The increased risk was demonstrated with Desogestrel™ and Gestodene™ .

To make things more confusing, it appears that third generation pills may be better than second generation in terms of heart disease protection. The same authors who published the DVT findings found the new pills did not increase the risk of heart attack compared with non-users. When compared to second generation pills, the new pills reduced the rate of heart attacks by two to three times. As well, small elevations in blood pressure rarely associated with second generation oral contraceptive use have not been demonstrated with the new pills. One study actually found third generation pills to be beneficial in raising the body’s “good” cholesterol (HDL), which has been linked to lower rates of cardiac disease.

Finally, the new birth control pills do not seem to have the negative effect on blood sugars that has been seen with second generation pills.

How does a woman decide?

Recently a letter written by the editor of The British Medical Journal (a highly influential publication) addressed the dilemma. It started, “Rarely can an article in the BMJ be so difficult to write....” The author was referring to advice he wanted to give doctors on prescribing third generation birth control pills. On the one hand, these new pills have been shown to increase the risk of blood clots in the legs compared to their predecessors. On the other hand, third generation pills offer reduced side effects and may reduce the risks of cardiac disease. How does a woman decide? In the end, it must be a personal, informed decision that she discusses with her doctor. Here are some guidelines:

Third generation pills using Desogestre™ and Gestodene™ should be used with great caution by women who:

have a history of DVTs or a strong family history of blood clots in the legs.